Evening Primrose Oil Benefits and Risks

Evening primrose has been studied for conditions related to menstruation and menopause like cyclical breast pain, premenstrual syndrome (PMS), hot flashes, and osteoporosis. It has also been studied to treat skin and inflammatory conditions. Research, however, does not support taking evening primrose oil as a treatment for any medical condition.

Evening primrose oil is extracted from the seeds of Oenothera biennis, a plant native to North America and South America. It gets its name from its yellow blossoms, which bloom in the evening. The oil contains linoleic acid, gamma-linolenic acid (GLA), and other omega-6 fatty acids.

Uses

The medicinal properties of evening primrose are not well understood. Some research suggests that the oil extracted from the seeds contains beneficial chemical components, including GLA, an omega-6 fatty acid.

The evidence for using evening primrose oil as a treatment is supported by small, preliminary studies and reviews of those studies. Some of these studies were done with GLA alone rather than evening primrose oil. The research is limited, and conclusions about its effects can’t be drawn yet.

Cyclical Breast Pain

Evening primrose oil has been studied as a way to treat cyclical breast mastalgia (pain) linked to the menstrual cycle (usually about a week before your period). However, the results of this research have been mixed.

In one study, participants were treated with evening primrose oil for two, three, six, or 12 months. The researchers concluded that the oil may be helpful for improving cyclic breast pain.

In a meta-analysis, researchers looked at 13 clinical studies comparing evening primrose oil to vitamin E, topical nonsteroidal anti-inflammatory drugs (NSAIDs), and danazol (a hormone). The researchers concluded that evening primrose oil was not better or worse than the other treatments for breast pain.

The researchers also reviewed five studies comparing evening primrose oil to a placebo (no treatment), one study comparing it to bromocriptine and danazol, and one study comparing it to vitagnus. The placebo studies suggested that evening primrose oil reduced pain better than placebo.  

In the bromocriptine and danazol study, 55% of the participants who took evening primrose oil reported less breast pain. In the vitagnus study, the average pain reported by participants decreased in the evening primrose oil group; however, the decrease was not significantly different from the treatment group.

Premenstrual Syndrome (PMS)

Evening primrose oil has been studied to treat PMS, a common group of symptoms linked to the menstrual cycle. Symptoms of PMS vary in severity and can include cramps and mood changes.

One review of research highlighted eight studies that compared evening primrose oil with a placebo for PMS and one study comparing GLA (an omega-6 fatty acid) with a placebo. The evening primrose oil study showed a significant decrease in PMS severity, while the GLA study showed a shortened duration and decreased severity of PMS.

Perimenopause and Menopause

Evening primrose oil has been studied to treat hot flashes during perimenopause, the transitional period to menopause.

Researchers compared black cohosh and evening primrose oil as treatments for hot flashes in 80 postmenopausal people. The severity of symptoms in both groups improved significantly after eight weeks, but black cohosh was more effective than evening primrose oil in reducing the number of hot flashes.

Another study compared evening primrose oil with a placebo. Though there was no noticeable effect on hot flashes, the study did show that the people in the evening primrose group reported fewer and less severe night sweats.

One six-week study compared evening primrose oil and a placebo in 56 menopausal people. Those who took the evening primrose had decreased severity of hot flash symptoms, improvement in social activities, and improvement in sexuality. Similar to the other studies, there was no decrease in the frequency of hot flashes.

Bone Health

Researchers are interested in the possible connection between unsaturated fat and a reduced risk of osteoporosis. Osteoporosis is a condition in which bone mineral loss causes the bones to get weak and brittle. The condition primarily affects people who have completed menopause.

Although omega-6 fatty acids are found in evening primrose oil, some studies have looked at the bone density effects of all polyunsaturated fatty acids, which include omega-3 and others.

In one study, researchers reviewed polyunsaturated fatty acids and bone mineral density. The review included an 18-month study of a combined treatment with evening primrose oil, fish oil, and calcium supplements. The results showed slowed or reversed bone loss in older people taking supplements compared to a control group who got a placebo.

In a large-scale genetics study, researchers looked at genetic information from several thousand people. They were looking for a connection between omega-6 fatty acids and bone mineral density. 

The study showed associations between fatty acids and bone mineral density but not omega-6 fatty acids. While this was a genetic study and not a clinical study of a treatment, it might be an avenue for future research.

Eczema

Eczema (atopic dermatitis) is a skin condition that causes scaly and inflamed skin. As part of a review of borage oil and evening primrose oil for eczema, researchers looked at 19 studies comparing evening primrose oil with a placebo. The studies found that evening primrose oil was not more effective for treating eczema than a placebo.

Acne

Acne, a condition in which pores get clogged with oil and dead skin cells, has also been treated with evening primrose oil.

One small, nine-month study had 50 participants add evening primrose oil to isotretinoin, a standard acne treatment. Twenty-five of the participants were given isotretinoin alone, and 25 were given evening primrose oil and isotretinoin. Improvement in acne was observed in both groups, and the group that took evening primrose oil also noticed additional skin hydration.

Psoriasis

Evening primrose oil and other sources of fatty acids are often studied for psoriasis, a condition that causes scaly and itchy patches of skin.

In one review, researchers looked at the effects of fatty acids, including evening primrose oil, on the processes in the body thought to be involved in psoriasis. The researchers found that evening primrose oil, linoleic acid, and other fatty acids were beneficial for psoriasis. However, the review did not provide specific information about how it could be used as a treatment.

Skin Appearance

Many skincare products use evening primrose oil and claim it helps with the look and feel of skin. An older study found that evening primrose oil appeared to increase skin firmness, elasticity, and hydration. More research is needed to determine whether evening primrose oil really has these benefits for the look and feel of skin.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease in which the immune system attacks and damages the joints. 

In one 12-week study, 60 participants with active rheumatoid arthritis were assigned to take fish oil, or fish oil and evening primrose oil. At the end of the study, both groups had improvements in disease activity score and the number of tender joints plus decreased pain.

Heart Health

Researchers have looked at whether evening primrose oil might have cardiovascular health benefits, but most of these studies have been in animals.

A 2014 study in rats modeled heart attacks in animals eating a high-fat diet. The rats were given evening primrose oil to see if it would help with some risks for heart attacks, like blood clots and high cholesterol.

While the study suggested that evening primrose oil might be beneficial for reducing these risks, studies in rats do not necessarily show what would happen in humans. High-quality research studies in humans would need to be done to find out whether evening primrose oil could have heart health benefits.

A review of studies that did include humans looked at whether evening primrose oil might help lower cholesterol. The review suggested that the supplement might help lower total cholesterol levels and raise HDL or “good” cholesterol levels. However, more research is needed to confirm the findings.

High cholesterol is a risk factor for cardiovascular disease. If evening primrose is proven to help lower cholesterol, that could be a potential heart health benefit. More high-quality research studies are needed.

Multiple Sclerosis

Multiple sclerosis is an autoimmune disease that affects the coverings of nerves in the brain and spinal cord. It can be relapsing (gets better, then worse) or progressive (continues to worsen).

In one study, researchers compared evening primrose oil and a placebo treatment in 52 people with multiple sclerosis. After three months, the researchers found that the treatment group reported improved pain, fatigue, and cognitive function compared to the placebo group.

However, conclusions cannot be drawn from this study alone because it was very small. 

Diabetic Neuropathy

Evening primrose oil has been studied as a possible treatment for diabetic neuropathy, a condition of nerve dysfunction resulting from long-term diabetes.

In a 12-week study, 73 participants with diabetic neuropathy took GLA, alpha lipoic acid, or a placebo. Both treatment groups reported decreased pain and total symptoms compared to the placebo group. However, there was not a statistically significant difference between the two treatment groups.

Another 12-month study used vitamin E and evening primrose oil to treat 80 people with painful diabetic neuropathy. The researchers concluded that evening primrose oil combined with vitamin E improved pain in 88% of the participants.

These studies were small and used combination treatments rather than just evening primrose oil, so the results are not significant enough to prove that evening primrose oil on its own can treat diabetic neuropathy.

Side Effects

There has not been much research on the long-term safety of evening primrose oil. Shorter studies have noted some side effects. 

Common Side Effects

Evening primrose oil may cause side effects such as:

• Stomach upset
• Bloating
• Headache
• Nausea and altered taste
• Diarrhea
• Seizure

Most of the side effects are mild and get better on their own once the treatment is stopped.

Severe Side Effects

Information about the severe side effects of using evening primrose oil is lacking. It’s possible that some people have serious side effects from a supplement like evening primrose oil. 

If you are using evening primrose oil and have signs of a severe allergic reaction like hives, cramping, and diarrhea, call 911 or go to the ER.

Precautions

Evening primrose oil should be used with caution if you have certain medical conditions. Always talk to your provider before starting any supplement, even one available over-the-counter (OTC). 

• Evening primrose oil may increase the risk of bleeding. If you have a bleeding disorder, be very careful if you use evening primrose oil. 
• If you will be having surgery, your provider may want you to stop taking evening primrose oil. Any medicine or herb that affects how your blood clots or increases the risk of bleeding should be stopped for at least two weeks before surgery. Ask your healthcare provider if you are not sure if you need to stop taking any of your medications or supplements before surgery.
• Although there is an ongoing study about evening primrose oil for the induction of labor in pregnancy, there is not yet enough evidence to make a recommendation. Always talk to your provider about taking any kind of supplement while you’re pregnant.
• It’s not clear if evening primrose oil is safe while you’re breastfeeding. Talk to your provider about any supplements you're considering if you plan to breastfeed.

It’s important to always tell your healthcare provider about all the supplements you take. They can help make sure they won’t interact with any medications or conditions you have. 

Dosage

The Food and Drug Administration (FDA) does not regulate supplements in the same way they regulate drugs. That means there are no universal guidelines regarding the appropriate use of evening primrose oil.

Evening primrose oil is generally considered safe for use in adults. There is no recommended dosage of evening primrose oil. Doses used in research studies ranged from 240 milligrams daily to 4 grams daily. If you take evening primrose oil every day, you might be more likely to have side effects.

Since there isn’t enough research to prove its safety, evening primrose should not be given to children or older adults without first asking a healthcare provider.

Interactions

Evening primrose oil can interact with several medications, either reducing the drug's efficacy or causing side effects, including:

• Anticoagulants (blood thinners) like Jantoven (warfarin)
• NSAIDs like diclofenac, ibuprofen, and aspirin
• Antipsychotic drugs like chlorpromazine (a phenothiazine drug)
  
• Human immunodeficiency virus (HIV) medications, such as lopinavir

It is essential to carefully read a supplement's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review the supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

Summary

Evening primrose oil comes from the seed of the evening primrose plant. It contains linoleic acid and GLA, which are omega-6 fatty acids.

Some studies have supported using evening primrose oil for some conditions that cause pain or inflammation. However, since the research is limited and has shown mixed, the claims about health benefits are not conclusive and well-supported. 

Evening primrose oil can be purchased as a dietary supplement at most pharmacies and health food stores. Talk about it with your healthcare provider first before trying evening primrose oil. Mention any medications you are taking and conditions you have (especially bleeding disorders) to make sure it’s safe for you.